Towards Water-Efficient Irrigation of Cup Plant ( Silphium perfoliatum L.) for Energy Production: Water Requirements and Rainfall Deficit

The cup plant shows promise for biomass production and has significant potential for increasing biodiversity. This species primarily grows in habitats with high soil humidity. Precipitation deficits are common throughout Poland, especially in the central regions, necessitating crop irrigation. To design and manage resource-efficient irrigation for the cup plant, estimating water requirements and rainfall deficits is essential. This research aims to calculate water requirements, rainfall deficits, and irrigation demand and to assess their temporal and spatial variations for cup plants energy plantations from 1981 to 2020. The study, conducted using the Blaney–Criddle method, focused on the growing season (1 April–30 September) across four provinces in central Poland: Kuyavian–Pomeranian (18°01′ E, 53°08′ N), Greater Poland (16°50′ E, 52°25′ N), Masovian (20°59′ E, 52°09′ N), and Lodz (19°24′ E, 51°44′ N). The research revealed varying values of water requirements depending on the province, ranging from 445.9 mm in Lodz province to 465.2 mm in Kuyavian–Pomeranian province. The magnitude of water requirements also significantly depended on the month of the growing season, with the highest value occurring in July (from 103.6 mm in Lodz province to 108.9 mm in Kuyavian–Pomeranian province). Over the forty-year period, a notable upward trend in water requirements was observed across all provinces, ranging from 6.7 mm per decade to 12.5 mm per decade. On average, rainfall deficits during the growing season amounted to 125 mm in normal years, 237 mm in medium dry years, and 316 mm in very dry years. These findings are crucial for efficient irrigation management in central Poland, which, in line with sustainable agricultural development, will enable the maximization of yields of this plant while simultaneously conserving water resources.